Repo Map

repo-map

Produces a ranked list of the structurally-important symbol definitions in a codebase, capped to a token budget. The point: instead of dumping whole files (wasteful, blows the context window), get a cheap "skeleton" of the repo — the functions/classes everything else depends on — and read full files only where it matters.

This is our zero-dependency port of Aider's repo-map.

When to use

• Onboarding to an unfamiliar or large codebase — get the lay of the land first.
• Before a refactor / deep-review / workflow-orchestration fan-out — feed each subagent the map so it knows the important entry points without re-scanning.
• JIT context (principle 07 / practice_context_engineering) — load the map, not the files.
• Anytime the instinct is "let me read 20 files to understand this" → run this first.

Usage

python scripts/repo_map.py [ROOT] [--budget-tokens N] [--top N] [--json] [--no-signature] [--max-files N]

• ROOT — repo root (default: cwd). If it's a git repo, only tracked files are scanned (honors .gitignore); otherwise a filtered directory walk is used.
• --budget-tokens (default 1024) — stop emitting once ~this many tokens are used (≈4 chars/token heuristic). Use 256–512 for a quick orientation, 2048+ for depth.
• --top N — hard cap on symbols before the budget applies.
• --json — machine-readable output (for piping into a workflow / another agent).
• --no-signature — emit path:line: name instead of the full signature line.

JSON distinguishes symbols_extracted_total (before --top), symbols_ranked_after_top (after that cap), and symbols_emitted (after the token budget). The legacy symbols_total key retains its post---top meaning for compatibility. None is a semantic coverage guarantee: extraction is regex-based and --max-files can limit input. Never diagnose parser coverage from a capped map.

Typical recipes

# Quick orientation in a new repo
python scripts/repo_map.py . --budget-tokens 512

# Feed a fan-out: JSON map of the most important 40 symbols
python scripts/repo_map.py /path/to/repo --top 40 --json > repo_map.json

# Focus a subdirectory (a single layer/service)
python scripts/repo_map.py /path/to/repo/services/auth --budget-tokens 800

How ranking works

1. Extract definitions (functions/classes/types) and identifier references per file via per-language regexes (py/js/ts/tsx/go/rust/java/ruby/c/cpp/csharp/php/kotlin/swift).
2. Build a directed graph: edge F → D when file F references an identifier defined in file D. Rare identifiers (defined in few files) weigh more.
3. Run PageRank over the file graph → structurally-central files float up (shared utilities, core models, base classes).
4. Symbol score = pagerank(def_file) × (1 + total_refs) × rarity. Emit highest first until the token budget is hit.

So the map surfaces the code everything else leans on, not just the first files alphabetically.

Gotchas

• Regex extraction, not tree-sitter. Fidelity is good for ranking but not a parser. Exotic syntax, heavy macros, or unusual formatting can miss/misattribute a def. This is a deliberate trade for zero-install + runs-anywhere. To upgrade fidelity, replace extract() with tree-sitter-language-pack tags — the graph/ PageRank stages stay identical. (Don't install tree-sitter casually: it trips the 7-day supply-chain gate; gate it like any fresh dep.)
• Token count is a heuristic (chars/4), not a real tokenizer. Treat the budget as approximate; it errs slightly high on code with many short tokens.
• Same name in many files (e.g. get, handle) ranks each def site separately — expected, since each is a distinct definition. Use --top to trim noise.
• Non-git dirs fall back to a denylist walk (node_modules, dist, venv, …). If your build output lives somewhere unusual, it may get scanned — point ROOT at the source dir instead.
• Generated code (protobuf, src/gen/) can dominate ranks because it's referenced everywhere. Point ROOT at hand-written source, or filter after the fact.

Troubleshooting

Verification

scripts/repo_map.py is stdlib-only and was verified to run on real trees (it correctly ranks shared-utility files to the top via PageRank). Re-run on any repo to confirm; there is no state to corrupt.